Production of Light (anti-)Nuclei with E864 at the AGS

Abstract

Light nuclei can be produced in the central reaction zone via coalescence in relativistic heavy ion collisions. E864 at BNL has measured the production of ten stable light nuclei with nuclear number of A=1 to A=7 at rapidity $y\simeq1.9$ and $p_{T}/A\leq300MeV/c$. Data were taken with a Au beam of momentum of 11.5 A $GeV/c$ on a Pb or Pt target with different experimental settings. The invariant yields show a striking exponential dependence on nuclear number over ten orders of magnitudes with a penalty factor of about 50 per additional nucleon. This penalty factor is used to estimate the strange quark matter (strangelet) production in the baryon rich and strangeness enhanced environment. The measurements of the production of antiproton, antideuteron, hypernuclei ($^{3}_{\Lambda}H$,$^{4}_{\Lambda}H$), and strongly unstable nuclear states ($^{4}H$,$^{5}Li$, $^{5}Li^{*}$, $^{5}He$) are presented as well. A model of local thermal equilibrium with radial flow at the kinetic freeze-out with a temperature of $T=112\pm10MeV$, chemical potential of $\mu_{B}=503\pm20MeV$ and flow velocity of about $\sqrt{V_{\perp}^{2}}\simeq0.5c$ seems to be able to describe the data in the gross scale with the exceptions of the production of antihyperons and hypernuclei. The large antihyperon production and the extra penalty for hypernuclei production are quite surprising.